U.S. patent number 4,492,314 [Application Number 06/594,058] was granted by the patent office on 1985-01-08 for reinforced tank wall structure for transformers.
This patent grant is currently assigned to Westinghouse Electric Corp.. Invention is credited to Randall N. Avery.
United States Patent |
4,492,314 |
Avery |
January 8, 1985 |
Reinforced tank wall structure for transformers
Abstract
A reinforced structure for resisting deflection of a tank wall
that is subjected to a range of positive and negative pressures
within the tank characterized by a plurality of closely spaced
braced members disposed in general alignment and mounted on the
tank wall so that upon limited deflection of the wall the brace
members move into contact and thereby increase wall resistance to
additional damaging deflection.
Inventors: |
Avery; Randall N. (Franklin
Park, PA) |
Assignee: |
Westinghouse Electric Corp.
(Pittsburgh, PA)
|
Family
ID: |
24377333 |
Appl.
No.: |
06/594,058 |
Filed: |
March 28, 1984 |
Current U.S.
Class: |
220/646;
336/90 |
Current CPC
Class: |
H01F
27/02 (20130101) |
Current International
Class: |
H01F
27/02 (20060101); B65D 007/42 () |
Field of
Search: |
;220/71,72,1B,3,85TC
;52/108 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Pollard; Steven M.
Attorney, Agent or Firm: Johns; L. P.
Claims
What is claimed is:
1. A reinforced wall structure for resisting deflection of a tank
wall that is subjected to a range of positive and negative
pressures within the tank, comprising:
(a) tank means for containing fluids and comprising a tank
wall;
(b) brace means on the tank wall for limiting inward and outward
deflections of the wall in response to pressure variations within
the tank means;
(c) the brace means including a brace member on the wall and having
a body portion including first and second surfaces with the first
surface being secured to the tank wall and the second surface being
spaced from the wall;
(d) the body portion having a plurality of narrow slots spaced
longitudinally and generally normal to the longitudinal axis of the
portion;
(e) each slot extending from the second surface and toward the
wall.
2. The structure of claim 1 in which the slots extend from the
second surface to the tank wall.
3. The structure of claim 1 in which the slots extend from the
second surface to a location between the first and second
surfaces.
4. The structure of claim 1 in which the brace member is mounted on
the outer surface of the tank wall.
5. The structure of claim 1 in which the brace member is mounted on
the inner surface of the tank wall.
6. A reinforced structure for resisting deflections of a tank wall
that is subjected to a range of positive and negative pressures
within the tank, comprising:
(a) tank means for containing fluids and comprising a tank wall;
and
(b) brace means mounted on the wall for stiffening the wall and
including a plurality of spaced brace members disposed in general
alignment so that upon limited deflection of the wall the brace
members move into contact to thereby increase wall resistance to
additional damaging deflection.
7. The structure of claim 6 in which the plurality of spaced brace
members are mounted in general alignment on the wall.
8. The structure of claim 6 in which the plurality of spaced brace
members are integral parts of an elongated member mounted on the
wall.
9. The structure of claim 8 in which the adjacent brace member
includes closely spaced, oppositely facing surfaces that move into
surface-to-surface contact upon limited deflection of the wall.
10. A reinforced wall structure for electrical equipment,
comprising:
(a) tank means for containing fluids and comprising a tank
wall;
(b) electrical equipment within the tank means;
(c) brace means on the tank wall for limiting inward and outward
deflections of the wall in response to fluid pressure variations
within the tank means;
(f) the brace means including a plurality of brace members disposed
in general alignment so that upon limited deflection of the wall
the brace members move into contact to thereby increase wall
resistance to additional damaging deflection.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a reinforcing structure for resisting
deflection of a tank wall that is subjected to a range of positive
and negative pressures within the tank, and more particularly it
pertains to a tank for a transformer.
2. Description of the Prior Art
Power transformers are the subject of constant design changes in
order to improve their cost and efficiency. In particular, large
tank structures for containing transformers are exposed to varying
temperature conditions incurred by internal and external
environments. Moreover, transformer tanks are subjected to wide
variations in pressure during testing and subsequent start-up
periods. For example, when a transformer tank is filled with a
dielectric coolant for a liquid-cooled transformer, the tank is
preliminarily evacuated to a pressure of about -14.7 psig in order
to minimize the gas content of the coolant. During subsequent
operation of the transformer the pressure on the tank often reaches
a pressure of about 8 psig. As a result a tank wall is subjected to
positive and negative pressures within the tank which has created
problems in designing transformers having lower cost and higher
efficiencies.
SUMMARY OF THE INVENTION
It has been found in accordance with this invention that a
reinforced wall structure for resisting deflections of a tank wall
subjected to a range of positive and negative pressures may be
comprised of a tank wall having bracing means on the wall for
limiting inward and outward deflections of the wall in response to
pressure variations thereon. The bracing means includes a brace
member on the wall for stiffening the wall and including a
plurality of spaced brace members disposed in general alignment so
that upon limited deflections of the wall, the brace members move
into contact to thereby increase wall resistance to additional
damaging deflections.
The advantage of the reinforced wall structure of this invention is
that it is conductive to a number of changes in internal design of
modern transformer which enable a reduction in the tank weight and
oil volume.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic view of a power transformer tank embodying
the reinforced wall structure of this invention;
FIG. 2 is a fragmentary view showing segmented braces having a
channel-like cross section located on a transformer tank wall;
FIG. 3 is a fragmentary view showing another embodiment of
segmented braces having nested channel-like cross sections;
FIG. 4 is a fragmentary view of another embodiment of segmented
braces having I-beam cross sections;
FIGS. 5, 6, 7, and 8 are sectional views through segmented braces
having varying cross sections;
FIG. 9 is a fragmentary sectional view showing a section of
segmented braces which are integral with an elongated member
attached to the tank wall; and
FIG. 10 is a sectional view showing segmented braces which are
separately attached to a tank wall.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The external features of a power transformer are shown in FIG. 1.
The reinforced wall structure of this invention is useful for tanks
of varying purpose where they are subjected to a range of positive
and negative pressures. For example, a power transformer is
generally indicated at 11 in FIG. 1 and it comprises a rectangular
tank having walls 13, 15, high-voltage bushings 17, low-voltage
bushings 19, cooling panels 21, and a top wall 23. The tank
contains a three-phase transformer which is enclosed within a
dielectric liquid coolant. A gas chamber is disposed above the
liquid coolant. The transformer structure, the liquid coolant, and
the gas are not shown in the drawing to facilitate the
illustration.
Heretofore, transformer tanks included wall structures that
accommodated positive and negative pressures for which purpose the
walls were too thick for deflection in and out, or had wall braces
for reinforcement in order to accommodate a large gas space above
the liquid coolant. A more recent trend in tank structure has been
to provide walls with more flexibility, whereby less gas space is
necessary due to wall bulging for which few, if any, wall braces
are required. However, the tank walls must withstand full vacuum
which is the real reason for wall braces. The tanks are made to
allow for thermal expansion of the fluid which, in turn, heats up
and compresses the gas (nitrogen) above the fluid. The current
tendency is to reduce the gas space at the top by letting the tank
bulge or deflect outwardly. By providing a reduced gas space
advantages are incurred including reduced cost, reduced shipping
weight, and reduced size which permits truck transportation as
compared with rail transportation. The more the tank walls bulge,
the less pressure created in the tank. The less pressure created,
the less tank strength is required which, in turn, is conducive to
more tank wall flexibility.
More particularly, the tanks are designed to accommodate a vacuum,
such as -14.7 psig, but at the same time being as flexible as
possible under positive pressure. Accordingly, the tank is designed
to accommodate a pressure range of from about 8 to about -15
psig.
In accordance with this invention, a tank wall is provided with
braces or brace members 25 which are adapted to restrain positive
and negative pressure on the tank wall. As shown in FIG. 2 braces
25 are comprised of channel members, preferably steel, which are
mounted at spaced locations between the top and bottom of the
transformer wall 15. The number of braces on a wall is dependent
upon such considerations as variations in wall thickness, and the
size of the wall. For example, since the pressure varies from about
8 to -14.7 psig, there should be about twice the number of braces
for negative pressure as that restraining the positive pressure.
Three braces (FIG. 2) are elongated channel members with the braces
25 having spaced slots 29 disposed at preferably equally spaced
locations around the longitudinal axis of the channel member. The
edges of the channel are secured, such as by welding, at 31 to the
tank wall along the entire length of the upper and lower legs of
the channel. The brace 27 is preferably unslotted and is similarly
secured, such as by welds 31, to the center of the tank wall.
However, the brace 27 may also be provided with slots 29 where
necessary, depending upon the thickness and size of the wall 15.
The slots 29 are narrow, having a width of about and may be
preferably provided by a saw blade.
Another embodiment of the invention includes nested braces 25, 33
(FIG. 3). Brace 33 has a preferably channel configuration of
smaller dimension than the brace 25 and includes legs which are
secured, such as by welding at 35 to the tank wall 15. The braces
33 are not slotted and provide the 1/2 strength necessary for
positive pressure. Braces 33 and slotted brace 25 act together
under negative pressure, doubling the strength of the bracing
system.
Another embodiment of the invention includes braces 37 (FIG. 4)
having spaced slots 39 similar to the slots 29. As shown, the
cross-sectional area of the braces 37 is that of an I-beam through
which the spaced slots 39 extend through the outer flange and
web.
Other embodiments of the invention are shown in FIGS. 5-7 which
include a brace 41 having a C-shaped configuration, a brace 43 of
solid bar configuration, an L-shaped brace 45, and a brace 47
having an inverted T-shape. All of the braces 41, 43, 45 are
slotted from their outer surface to locations 49 which are spaced
from the inner surface welds 51 where the braces are mounted on the
tank wall 13.
In accordance with this invention the several slots 29 have two
configurations. One configuration comprises slots extending from
the outer surface, such as surface 53, to a location 55 (FIG. 5) in
the C-brace 41. This leaves an unslotted brace portion 57 adjacent
to the tank wall 13 which is continuous throughout the length of
the brace from one end to the other. This unslotted portion is used
to facilitate handling, alignment and welding.
Another configuration of the slots 29 comprises slots extending
from the outer surface of the brace to the tank wall 13, leaving no
unslotted portion of the brace (FIG. 8). Thus, each brace, whatever
its configuration, has segmented separate portions which are
separately mounted, such as by welding at 51, (FIG. 8) onto the
tank wall 13.
As shown in FIG. 9 where the slots 29 terminate at a location 55
spaced from the surface of the wall 13 for the channel braces 25,
the non-slotted portion 57 remains as a reinforcing part of the
brace and operates primarily to reinforce the wall when a positive
pressure within the wall deflects the wall outwardly. In other
words, the non-slotted portion 57 of the braces reinforces the tank
wall 13 in response to positive pressure within the tank.
Where, however, the slots 29 extend all the way through the several
braces to the surface of the tank wall (FIG. 10), there is no
unslotted portion 57 left to function as reinforcement for the tank
wall 13 when it is deflected outwardly in response to a positive
pressure within the tank.
In response to a negative pressure within the tank, when the tank
wall 13 is deflected inwardly, the wall 15 bulges or is deflected
inwardly the slots close. That is, the closely spaced, oppositely
facing surfaces 59, 61 of adjacent brace segments 63, 65, 67 are
brought into contact, such as at 69 (FIG. 10), due to slight
shifting or movement of the segments 63, 65, 67, as shown by the
broken line positions of those segments. Similarly, as shown in
FIG. 9 the brace segments are brought together at contact points 71
in response to rotation of the brace segments when the wall 15
deflects inwardly in response to a negative pressure or vacuum
condition within the tank.
Accordingly, when limited deflection of the wall occurs the brace
segments move into contact to thereby increase wall resistant to
additional damaging deflection.
In the embodiment shown in FIG. 9 in which the slots extend only
partially through the braces, the unslotted portion of each brace
resists further deflection of the tank wall. However, where the
slots extend completely through the braces to provide separate
spaced brace segments, the wall per se serves as a positive
pressure restrainer and the separate braced segments 63, 65, 67
serve to accommodate the larger problem of wall resistance to a
vacuum within the tank during testing and filling of the tank with
dielectric coolant.
It is understood that the braces may be mounted on the interior
surface of the tank walls, whereby the completely slotted or
partially slotted segments function in a similar manner to prevent
outward bulging of the tank. Such a condition could obtain where
conditions such as tank wall thickness and/or size require the
interior mounting of the braces.
In conclusion, the use of a slotted or sawn tank brace, either by
itself or nested with another conventional brace, allows for a
differential stiffness. Under positive pressure the brace readily
deforms (where the braces are on the exterior wall surface), and
the slots will open up. The ease with which this deformation occurs
allows additional volume for the oil expansion. The brace will
seemingly not be there. The tank will be suitable only for a
positive pressure of 8 psig. On the other hand, under negative
pressure, the outer flanges of the slotted brace is under
compression. The slot closes and the brace is rigid and resists any
further deflection. With the extra strength of the slotted braces,
the tank easily withstands full vacuum requirements.
* * * * *